If you live in a climate where the outdoor air is generally fairly dry and also sufficiently warm that it spends most of its time above the interior dewpoint, then fine. You can vent our attic and it stays dry. This covers rather little of the world.
If you do not insulate at all and you heat your house when it’s cold or wet and you do not experience hot and humid weather, then there will be enough heat flow to keep your attic dry. This is generally an awful idea, but old insulated houses did work in many climates.
If you live somewhere cold and put fluffy stuff on your ceiling and you vent your attic and you have air leaks in your ceiling (hint: this is basically unavoidable) and it’s very cold in your attic, you may get condensation in the ceiling insulation or the attic. Mold time.
If you live somewhere hot and humid and you vent your attic, then you are are filling your attic with hot, humid air. Your dehumidifier or A/C will not control your attic humidity. But your A/C may cool parts of your attic, leading to additional condensation.
If you have nasty severe blowing rain, it may blow into your attic, leading to damage. This is a problem in hurricanes.
Wildfire embers can ignite the inside of your attic. You can try to use fancy supposedly ember resistant vents to mitigate this, or you can omit vents entirely.
If you seal your attic and control moisture in the living spaces well enough to avoid moisture problems and you have adequate conditioning in your attic, your attic will be about the same temperature and humidity as your living spaces, and you’ll be fine.
You can geek out at buildingscience.com. The author appears to have become increasingly convinced that vented attics are basically never the answer.
alt Hacker News
Au contraire.
If you live in a climate where the outdoor air is generally fairly dry and also sufficiently warm that it spends most of its time above the interior dewpoint, then fine. You can vent our attic and it stays dry. This covers rather little of the world.
If you do not insulate at all and you heat your house when it’s cold or wet and you do not experience hot and humid weather, then there will be enough heat flow to keep your attic dry. This is generally an awful idea, but old insulated houses did work in many climates.
If you live somewhere cold and put fluffy stuff on your ceiling and you vent your attic and you have air leaks in your ceiling (hint: this is basically unavoidable) and it’s very cold in your attic, you may get condensation in the ceiling insulation or the attic. Mold time.
If you live somewhere hot and humid and you vent your attic, then you are are filling your attic with hot, humid air. Your dehumidifier or A/C will not control your attic humidity. But your A/C may cool parts of your attic, leading to additional condensation.
If you have nasty severe blowing rain, it may blow into your attic, leading to damage. This is a problem in hurricanes.
Wildfire embers can ignite the inside of your attic. You can try to use fancy supposedly ember resistant vents to mitigate this, or you can omit vents entirely.
If you seal your attic and control moisture in the living spaces well enough to avoid moisture problems and you have adequate conditioning in your attic, your attic will be about the same temperature and humidity as your living spaces, and you’ll be fine.
You can geek out at buildingscience.com. The author appears to have become increasingly convinced that vented attics are basically never the answer.